Agricultural vehicles often times have hitches that can be used to tow implements or trailers. These hitches may be of the drawbar type or three-point type. Often times, attaching these implements to a vehicle may be tedious, since it requires positioning the vehicle quite accurately, and making small adjustments to the position, perhaps as small as several millimeters.
A new type of transmission is available on many agricultural tractors, typically termed a “continuously variable transmission” or CVT. This type of transmission differs from other transmissions in that there is a continuous range of gear ratios available, rather than a discrete number of fixed ratios. Often times, the operator commands the direction of the travel and the ground speed, and the speed is regulated electronically. In order to control the true ground speed, the tire size must be known and is often entered by the operator or technician. If this is not desired, the axle speed may be regulated, or alternatively, the gear ratio may be set by the operator. Some agricultural vehicles, such as tractors, may have automatic features to control the engine speed and optimize various parameters. Vehicles with CVTs often include a feature that controls the speed of the vehicle to be zero. However, control loops used to maintain the velocity to zero will have some error and cause slow drift. This control of velocity can be effectuated by a pedal on the floor and/or a handle within reach of the operator of the tractor.
One example of a CVT transmission is the four range, common input, inline pump/motor transmission described in U.S. Pat. No. 7,063,638, whose disclosure is incorporated by reference herein in its entirety. Such a transmission uses a variable hydraulic pump and motor to achieve continuous variation of the gear ratio.
In order to control the speed, it is conventionally known to have a transmission, such as a powershift transmission or a CVT transmission, operably connected to an inching pedal. These inching pedals are utilized for making small adjustments to the speed of the agricultural vehicles by depressing the inching pedal to slow down or stop the vehicle. When the inching pedal is depressed, this releases the pressure in a clutch in the transmission, which results in slippage of the clutch and less torque being transferred through the transmission. Such systems permit the use of the inching pedals with full engine speed available for lifting or other purposes. The direction of inching can be set by the direction that the transmission is commanded to operate in. For example, the direction of the transmission may be controlled by a lever with a forward, reverse, neutral and perhaps park positions, where the movement can be controlled to be in a forward direction, in a reverse direction, or neither if the vehicle is stopped. The forward and reverse positions of the lever can be selected for inching in the forward or reverse directions, respectively, and the inching pedal would be used to control the speed of the vehicle as the inching is performed.
While existing systems permit the provision of a gear ratio or ground speed for positioning the agricultural vehicle to attach an implement, there is a need for a vehicle where the operator can directly command a change in the position of the vehicle in order to provide more control of exactly where the vehicle will be. The present invention addresses this need, as explained below.